13 “You have visited the earth, and hast inebriated it”. Whence hast inebriated the earth? “Your cup inebriating how glorious it is!” “You have visited the earth, and hast inebriated it.” You have sent Your clouds, they have rained down the preaching of the truth, inebriated is the earth. “You have multiplied to enrich it.” Whence? “The river of God is filled with water.” What is the river of God? The people of God. The first people was filled with water, wherewith the rest of the earth might be watered.
Hear Him promising water: “If any man thirst, let him come to Me and drink: he that believes in Me, rivers of living water from his belly shall flow:” if rivers, one river also; for in respect of unity many are one. Many Churches and one Church, many faithful and one Bride of Christ: so many rivers and one river. Many Israelites believed, and were fulfilled with the Holy Spirit; from thence they were scattered abroad through the nations, they began to preach the truth, and from the river of God that was filled with water, was the whole earth watered.
“You have prepared food for them: because thus is Your preparing.” Not because they have deserved of You, whom You have forgiven sins: the merits of them were evil, but You for Your mercy's sake, “because thus is Your preparing,” thus “You have prepared food for them.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)